This study will examine the role of diet in the etiology of prostate cancer. The dietary heterogeneity of Hawaii's multi-ethnic population offers a special opportunity to conduct such a study. Three separate dietary components will be included in a case-control design: 1) fats, 2) cadmium/zinc, and 3) vitamin A. Cases with a histologically-confirmed diagnosis of prostatic carcinoma will be identified for the period 1978-1983 through major hospitals on the island of Oahu. Each case will be matched on age and sex with two population controls. A dietary history, specifically designed to assess the food components of interest to this study, will be administered by trained interviewers to each study subject at his home; in addition, a hair sample will be collected from each subject. A total of 486 cases and 972 controls will be interviewed over the 3-year period of the study. Dietary intakes of fat (total fat, saturated fatty acids, etc), trace elements (zinc and cadmium) and vitamin A (both the preformed vitamin and its precursors) will be computed from the food histories and compared between cases and controls. The cadmium and zinc content of the hair samples will be correlated with the results from the diet histories. Few data are presently available on the possible association of diet and prostate cancer. This study should contribute useful information on that subject.